West Pacific/2015/11W/Archive/14
Public advisory TYPHOON NANGKA PUBLIC ADVISORY NUMBER 14 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST TUE JUL 07 2015 ...NANGKA SLOWS IN INTENSIFICATION... SUMMARY OF 12:00 AM JST...15:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...12.4N 157.5E CENTER POSITION CONFIDENCE: HIGH ABOUT 815 MI...1,310 KM ESE OF SAIPAN, MARIANA ISLANDS MAXIMUM SUSTAINED WINDS...90 KT...105 MPH...165 KM/H MINIMUM BAROMETRIC PRESSURE...958 MB...28.29 INCHES PRESENT MOVEMENT...W AT 11 KT...13 MPH...21 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 12:00 am JST, the center of Typhoon Nangka was situated near 12.4N, 157.5E, or about 815 miles (1,310 km) east-southeast of Saipan, Mariana Islands. Maximum sustained winds were 90 knots (105 mph, 165 km/h), with higher gusts. The minimum barometric pressure was 958 millibars (hPa; 28.29 inHg), and the cyclone was tracking west-northwest at 11 knots (13 mph, 21 km/h). Additional intensification is expected over the next 48 hours as Nangka remains steady in trajectory. NEXT ADVISORY ------------------- Next complete advisory at 6:00 am JST. $$ Forecaster TAWX14 Discussion TYPHOON NANGKA DISCUSSION NUMBER 14 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST TUE JUL 07 2015 Typhoon Nangka has improved slightly in organization since the previous special advisory. Although still misshapen, the eye has become slightly smaller since earlier and its temperature has warmed to approximately 10°C. Meanwhile, deep convection has expanded in coverage across the southern eyewall. A recent AMSU pass indicates that the western portion of the eyewall has deteriorated some from earlier; this may be the result of mid-level dry air to the cyclone's west. Given the constrained estimates of T4.5/77kt from JTWC and T5.0/90kt from SAB, as well as the recent estimate of T5.5/102kt from UW-CIMSS ADT, the initial intensity has been edged upward to 90kt. The intensity forecast is a little more complicated than the previous advisory suggested. Water vapor animations and maps from UW-CIMSS indicate that the upper-level winds atop Nangka have increased to a moderate 10 to 20 knots from the northwest. This increase in shear was well forecast by the GFS. As such, only steady intensification is forecast for the next 72 hours or so. Thereafter, as the typhoon approaches the northern Mariana Islands, the environment is once again forecast to become favorable for a more rapid pace of intensification. However, it is worth noting that the structural changes that occur within the inner core of powerful cyclones are not well forecast, and such changes could ultimately influence Nangka's intensity at any time. By the end of the forecast period, although sea surface temperatures and ocean heat content are expected to remain favorable, an increase in wind shear may slow further development. Nangka continues to track swiftly west-northwestward. This motion is expected to continue for the next 72 hours or so as the cyclone is guided along the southwestern periphery of a mid-level ridge across the northern West Pacific. Thereafter, the approach of a mid- to upper-level trough across northern Japan is expected to erode the western edge the ridge and allow Nangka to track more poleward at a slower rate. Model guidance has shifted southward in the short term compared to yesterday, and the updated track forecast once again is nudged in that direction. On the forecast path, Nangka poses a greater risk than ever to the northern Mariana Islands, and residents there should monitor the progress of what is expected to become a super typhoon over the coming days. INIT 06/1500Z 12.4N 157.5E 90 KT 105 MPH 12H 07/0000Z 13.1N 155.1E 95 KT 110 MPH 24H 07/1200Z 13.8N 153.2E 100 KT 115 MPH 36H 08/0000Z 14.9N 151.4E 105 KT 125 MPH 48H 08/1200Z 16.2N 149.5E 110 KT 120 MPH 72H 09/1200Z 18.9N 145.6E 120 KT 140 MPH...NEAR NORTHERN MARIANA ISLANDS 96H 10/1200Z 20.3N 143.2E 130 KT 150 MPH...NEAR NORTHERN MARIANA ISLANDS 120H 11/1200Z 21.8N 141.0E 135 KT 155 MPH $$ Forecaster TAWX14